Well, as long as the width is divisible by 4, you can cut it in a grid. Which is the case here. I didn't find the one you mentioned that is 161px X 85px, which one is that?
On my side, all of their widths are multiples of 2, so they are divisible by 4, hence usable in a grid system.
The pack provides the sprite only, not sprite sheets, or atlases. The sprite sheet creation is to be handled on your side, maybe the unity tool is not a good fit with the Magicavoxel exports, there surely are other tools out there for sprite sheet creation.
Maybe that can help :